Commercial Vacuum Research Articles

Investigating the Commercial Microwave Vacuum Drying Conditions on Physicochemical Properties and Radical Scavenging Ability of Thai Green Tea

The effects of drying conditions using a commercial microwave vacuum dryer on the physicochemical properties and antioxidant activity of Thai green tea were investigated. Nine different drying conditions (power 3200, 3600, and 4000 Watts vs. radiation time 20, 25, and 30 min) were applied in this study. The results showed that individual catechins, their total quantities, radical scavenging ability, and moisture content were significantly affected; however, total polyphenol content and color parameters were not significantly affected by these drying conditions. Based on this data, to obtain optimal physicochemical properties of green tea, drying conditions at 3600 Watts for 30 min were recommended.

A novel approach for reduction of electric field stress in vacuum interrupter chamber using advanced soft computing algorithms

This investigation presents a new algorithm for optimized internal shape design of high voltage equipments like a vacuum interrupter (VI) chamber, regarding to electric field intensity distribution pattern. At first a commercial vacuum chamber is modeled using Solid-Works and Comsol-Multiphysics softwares. The model design parameters are changed randomly to generate a new structure which is analyzed using finite element (FE) method to obtain 8 regions with maximum electric field intensity. This loop continues some times to arrange a data bank from input parameters vector and coupled output matrix for 8 internal electric field intensity components. The next stage is to train a suitable general regression neural network (GRNN) for every electric field output, separately, to form an objective functions with 8 objective components. Regarding the constrains and inequality conditions specified, a multiobjective genetic algorithm (GA) is arranged to run. A set of non-dominated points, called Pareto Front, are specified by this optimization algorithm which are edited and clustered in five sets using k-mean statistical function. In every set the point with smallest distance from the center point of that set is elite for final modeling and validation check. So the final optimized point is specified after F.E. modeling. This algorithm is studied in the case that the main shield is considered float. In continue we analyze the electric field reduction percentage achieved, which causes lower electric field stress on the insulators especially on the contact surfaces region. With respect to Fowler-Nordheim (FN) equation lower electric field causes lower field emission currents especially at the insulation recovery interval which increases the endurable transient recovery voltage (TRV) level of the chamber. Furthermore and in the future works the maximum size reduction of a vacuum interrupter chamber, or other equipment, can be performed with small change in the introduced algorithm.

Three-Dimensional Time-Dependent Model and Simulation of High-Current Vacuum Arc in Commercial Axial Magnetic Fields Vacuum Interrupters

With a quasi-steady 3-D MHD model, time-dependent axial magnetic field vacuum arcs (AMFVAs) characteristics in commercial vacuum interrupters for half-wave interruption of power-frequency (50 Hz) current are simulated. In a current time-dependent simulation, the influence of AMF lagged from arc current is considered in the arc model. 3-D spatial distributions of many important plasma parameters and electrical characteristics in AMFVAs can be obtained, such as ion number density, ion temperature, electron temperature, plasma pressure, current densities along different directions ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$x$</tex></formula> , <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$y$</tex></formula> , and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$z$</tex></formula> ), electric fields strength along different directions, and so on. Simulation results show that there exists a significant spiral-shaped rotational phenomena in the AMFVAs and the rotational velocity at the moments (9, 8, 7, and 6 ms) after 5 ms (the current peak value moment) is always larger than that before 5 ms (1, 2, 3, and 4 ms) because of the lagged AMF. This kind of plasma rotational phenomena also can be observed by high-speed arc photographs. In the future, the asymmetric appearance in high-current vacuum arc will be simulated based on a 3-D model.

Numbers of E. coli, non-O157 STEC, F-RNA coliphage, rotavirus, bovine enteric calicivirus on commercial vacuum packaged beef

Numbers of E. coli, non-O157 STEC, F-RNA coliphage, rotavirus, bovine enteric calicivirus on commercial vacuum packaged beef

Numerical Study on the Removal of Hydrogen and Nitrogen from the Melt of Medium Carbon Steel in Vacuum Tank Degasser

The steelmaking field has been seeing an increased demand of reducing hydrogen and nitrogen in liquid steel before casting. This is often accomplished by vacuum treatment. This paper focuses on developing a numerical model to investigate the removal of hydrogen and nitrogen from the melt of medium carbon steel in a commercial vacuum tank degasser. An activity coefficient model and the eddy-cell expression are implemented in the ANSYS FLUENT code to compute the activities of related elements and mass transfer coefficients of hydrogen and nitrogen in liquid steel. Several cases are simulated to assess the effect of gas flow rate and initial nitrogen content in liquid steel on degassing process and the calculated results are compared with industrial measured data.

Electrical Properties of Nanocrystalline CuCr25 Contact Material

Four pieces of nanocrystalline CuCr25 contacts with 45-mm diameter and 3-mm thickness were prepared, brazed onto cup-axial magnetic field electrodes, and assembled in two commercial vacuum interrupters to test their chopping current, ac dielectric breakdown voltage, and breaking capacity. For comparison, two microcrystalline CuCr25 contacts were also prepared as above. The test vacuum interrupters were operated by a 24-kV circuit breaker with a spring-operated mechanism. The opening velocity was 1.3 m/s and the arc current frequency was about 50 Hz. The experimental results showed that both the chopping current and the ac dielectric breakdown voltage of nanocrystalline CuCr25 contact material were lower than those of the microcrystalline CuCr25 material. The breaking capacity of nanocrystalline CuCr25 material was significantly lower than that of microcrystalline CuCr25. The cathode and the anode contact surfaces of nanocrystalline CuCr25 were seriously eroded by arc in the local areas, and obvious cracks occurred.

Assessment of penetration through vacuum cleaners and recommendation of wet cyclone technology

In many commercial vacuum cleaners, the captured aerosol particles contained in the dust collector may accidentally release from the exhaust filtration owing to leakage or penetration. Vacuum cleaners may cause dust to become airborne by exhausting air that is not completely filtered. This may cause the operator to inhale dust, in turn causing health problems. This study aimed to investigate the dust penetration rates from three commercial vacuum cleaners and suggest the best technique for completely filtering exhaust air using a combination of cyclonic separation and water filtration. The commercial vacuum cleaners were tested inside a custom-built hood, and the exhausted particles were monitored using a sampling probe in conjunction with an aerosol particle sizer. Quartzose mineral dusts were added to each vacuum cleaner through the dust transport line. A 2400 L/min wet cyclone was employed as the proposed vacuum cleaner. It was designed using Stokes scaling, and its collection characteristics were evaluated using polystyrene latex beads. Surprisingly, the conventional vacuum cleaners failed to capture an overall average of ˜14% of the particles in the given size range. However, only ˜3.8% of the collected particles escaped from the vacuum cleaner that used the wet cyclone technology. Thus, the proposed vacuum cleaner should potentially be an effective method for vacuuming household dust. Implications: The successful investigation of conventional vacuum cleaners is useful for both manufacturers and users. As an effective vacuum cleaning mechanism, household dust is able to migrate along the thin water film that forms on the inner walls of the cyclone vacuum cleaner. It collects dust in a small water inflow (3 mL/min), which allows it to capture a higher percentage of contaminants than most of the currently available vacuum cleaners. The significantly low accidental exposure rates achieved by this new vacuum cleaner enable healthy conditions in various environments, including indoors.

Development of a High Efficiency Degassing System for Making Silicone Rubber Mold

Silicone rubber mold is regarded as an important method of reducing the cost and time to market in a new product development process. Commercial automatic vacuum machine is widely used to degas in the manufacturing of silicone rubber mold, but the cost of hardware is very expensive. A high efficiency degassing system is designed and implemented from regular vacuum machine. It is found that degassing process includes explosion phase, balance phase and convergence phase. The maximum saving in the degassing time is about 63.7%. The advantages of this system include reducing human error of operator, reducing noise and air pollutions derived from the vacuum pump.

Survival of Arcobacter butzleri on vacuum packaged chill stored beef

The ability of Arcobacter butzleri to survive and the effect of initial cell numbers on their survival on vacuum packed chill stored beef were examined. In addition, the effect of natural microflora present on commercial beef on the survival of A. butzleri under vacuum packaged chill stored conditions was also examined. The numbers of A. butzleri on sterile beef cores stored under vacuum packaged conditions at −1.5 or 4°C dropped significantly (P<0.05) over the time of the study (6wks). In contrast, survival of A. butzleri on commercial vacuum packaged beef (beef with natural microflora) was significantly (P<0.05) enhanced, resulting in only 0.3 and 1.3logcfucm−2 drops in numbers at −1.5°C and 4°C, respectively, at the end of 6wks. Survival of A. butzleri on sterile beef cores inoculated with higher initial numbers was significantly (P<0.05) higher than on core inoculated with lower initial numbers, while on commercial vacuum packaged beef initial A. butzleri numbers had no significant (P>0.05) effect on its survival. Cores inoculated with ~106cfucm−2A. butzleri, irrespective of storage temperature or packaging conditions, could be enumerated by direct plating up to day 35. However, cores inoculated with ~104cfucm−2, irrespective of packaging conditions, A. butzleri could be enumerated by direct plating up to 28 and 21days from cores held at −1.5 and 4°C, respectively. On commercial vacuum packaged beef, irrespective of initial inoculated A. butzleri cell numbers or temperature of storage, A. butzleri could be enumerated by direct plating even at 6wks (end of the study). The presence of inoculated A. butzleri on commercial vacuum packaged beef, irrespective of the initial cell numbers had no significant (P>0.05) effect on the natural microflora numbers compared to uninoculated controls. These results show that natural microflora on commercial vacuum packaged beef afford enhanced survival of A. butzleri, irrespective of their initial cell numbers on the surface of beef stored at industry standard vacuum packaging and chill stored conditions. These findings reinforce the requirement for strict hygienic practices or the implementation of decontamination technologies to ensure safety of beef with respect to this pathogen.

The structure and mechanical properties of as-cast Ti–25Nb–xSn alloys for biomedical applications

The effects of tin on the structure and mechanical properties of a Ti–25Nb-based system were studied with an emphasis on improving the strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti–25Nb and a series of Ti–25Nb–xSn (x=1, 3, 5, 7, 8, 9, 10, 11, 13, and 15wt%) alloys prepared using a commercial arc-melting vacuum pressure casting system were investigated. The experimental results showed that the as-cast Ti–25Nb has an α″ phase, and when 1–5wt% Sn was introduced into the Ti–25Nb alloy, the structure remained essentially unchanged. However, with 7–15wt% Sn, retention of the metastable β phase began. Among the developed Ti–25Nb–xSn alloys, all the alloys had good ductility, and Ti–25Nb–8Sn and Ti–25Nb–9Sn alloys had lower bending moduli (52 and 53GPa, respectively) than c.p. Ti (99GPa) and the other Ti–25Nb-based alloys (61–133GPa). Moreover, Ti–25Nb–9Sn and Ti–25Nb–11Sn alloys exhibited higher bending strength/modulus ratios, as large as 20.5 and 20.6, respectively, higher than those of c.p. Ti (8.5) and the Ti–25Nb alloys (19.8). The Ti–25Nb–10Sn (41°) and Ti–25Nb–11Sn (46°) alloys had superior elastically recoverable angles, about 17.0 and 15.2 times greater than that of c.p. Ti, respectively. In the current search for a better implant material, β-phase Ti–25Nb-(8–11)Sn alloys show considerable promise due to their low moduli, ductile properties, excellent elastic recovery capability, reasonably high strength (or high strength/modulus ratio), and better shape memory effect.

Composites of Nanoporous Gold and Polymer

Experimental investigations of the strength of small objects – such as micropillars or nanowires – often point towards a trend of increasing strength with decreasing dimension,1–3 approximating the theoretical shear strength when the size drops to the lower nanometer region.1–4 The observation of theoretical strength in defect-free crystals, such as whiskers, irrespective of their size exemplifies that the trend of smaller is stronger is related to the defect structure.5–7 The interaction of dislocations with the surface is another important factor, as is evidenced by in situ observation of large recoverable flow-stress changes during interfacial charging or electrosorption.8 Irrespective of its microscopic origin, the high strength at small size suggests a search for design strategies that yield high-strength materials exploiting the mechanical properties of metal nanostructures. A key challenge, namely assembling many (1018 for 1 cm3 of material with a 10 nm structure size) nanoscale objects into a macroscopic body, can be overcome by synthesis via dealloying.9–11 The process provides millimeter- or centimeter-sized monolithic samples consisting of a homogeneous network structure of nanoscale “ligaments” with uniform size that can be controlled down to well below 10 nm.12, 14 Investigations by transmission electron microscopy, focused ion beam imaging, and electron backscatter diffraction have established that nanoporous metals prepared in this way are polycrystalline with a grain size of 10–100 μm.15, 16 Each micrometer-sized grain is nanoporous, so that neighboring ligaments share the same crystal lattice. In other words, the local structure in volumes of, say, 1 μm3, is that of a single crystal containing a contiguous nanoscale pore network. The mechanical behavior of these materials obeys scaling equations derived for foams with macroscopic porosity, and the local strength of the ligaments follows the same3, 17–19 or similar16, 20 trends as individual nanowires. The material, and in particular nanoporous gold (npg), has thus been studied as a model system for size-effects on the plasticity of nanostructures.

Laserspray ionization imaging of multiply charged ions using a commercial vacuum MALDI ion source.

This is the first report of imaging mass spectrometry (MS) from multiply charged ions at vacuum. Laserspray ionization (LSI) was recently extended to applications at vacuum producing electrospray ionization-like multiply charged ions directly from surfaces using a commercial intermediate pressure matrix-assisted laser desorption/ionization ion mobility spectrometry (IMS) MS instrument. Here, we developed a strategy to image multiply charged peptide ions. This is achieved by the use of 2-nitrophloroglucinol as matrix for spray deposition onto the tissue section and implementation of "soft" acquisition conditions including lower laser power and ion accelerating voltages similar to electrospray ionization-like conditions. Sufficient ion abundance is generated by the vacuum LSI method to employ IMS separation in imaging multiply charged ions obtained on a commercial mass spectrometer ion source without physical instrument modifications using the laser in the commercially available reflection geometry alignment. IMS gas-phase separation reduces the complexity of the ion signal from the tissue, especially for multiply charged relative to abundant singly charged ions from tissue lipids. We show examples of LSI tissue imaging from charge state +2 of three endogenous peptides consisting of between 1 and 16 amino acid residues from the acetylated N-terminal end of myelin basic protein: mass-to-charge (m/z) 795.81 (+2) molecular weight (MW) 1589.6, m/z 831.35 (+2) MW 1660.7, and m/z 917.40 (+2) MW 1832.8.

Recycling of waste plastics into fuels. LDPE conversion in FCC

In order to study the tertiary recycling of waste polymers in standard FCC units low density polyethylene (LDPE) was dissolved into a commercial vacuum gas oil at 2 and 6wt.% and converted over two equilibrium FCC catalysts of the octane-barrel and resid types in a CREC Riser Simulator laboratory reactor. The reaction temperatures were 500, 525 and 550°C, the mass catalyst to oil relationship was 6.35 and the contact times were from 3 to 30s. The study included the effect of the concentration of LDPE over conversion, the various product (dry gas, LPG, gasoline, LCO and coke) yields and selectivities. Results were very similar for the two concentrations. At typical conversions of 70wt.%, dry gas and gasoline yields increased about 10wt.%, LPG yields between 9 and 13wt.%, LCO yields decreased more than 15wt.% and coke yields were lower than 7.7wt.% The RON index of gasoline was improved slightly (up to one point), mainly due to significant increases in olefin concentrations, while the fuel quality of the LCO cut was not affected. LDPE is easily converted and seems to be subjected to primary reactions of catalytic cracking, thus increasing the yields of olefins in the LPG and gasoline boiling ranges. It was concluded that recycling waste LDPE by co-processing it as part of conventional feeds to the FCC would not interfere with the standard operation.

Spectroscopic Evidence for Atmospheric Stabilization of Aluminum Borohydride in Polydimethylsiloxane Grease

Raman and infrared vibrational spectroscopy were used to confirm the presence of aluminum borohydride dissolved in a commercial polydimethylsiloxane vacuum grease at room temperature. Spectroscopic evidence for an adduct between the aluminum borohydride and polydimethylsiloxane is also presented. Once dissolved in the polydimethylsiloxane grease, the aluminum borohydride was stabilized with respect to its usual pyrophoric reactivity in wet or dry air.

Detection of cheese packaging containment failures using reversible optical oxygen sensors

This study investigated the capacity of optical oxygen sensors to nondestructively detect containment packaging failures in commercial vacuum packed cheddar cheese. Unacceptable oxygen levels in packs lead to product deterioration and can significantly reduce shelf life. Vacuum packed cheddar cheese was monitored for oxygen levels over time at 4 °C with optical sensors prefitted to packaging laminates polyethyleneterephthalate/polypropylene. Oxygen levels present in packs immediately after packaging were 3% on average. Further ingress of oxygen into all packs occurred over storage time and levels ranged from 3.6% to 8.2% after 6 days. Information obtained using oxygen sensors led to further assessments and identification of the causes of packaging containment failure.

Effect of Lump Partitioning on the Accuracy of a Commercial Vacuum Gas Oil Hydrocracking Model

In an industrial hydrocracking plant, except to the reactor, the separation section can affect the accuracy of the developed mathematical model. In this study, two combined-bed six and seven-lump kinetic models for the hydrocracking of vacuum gas oil in a real refinery are developed and their accuracies for the prediction of product yields are compared. In the six-lump model, the engaged components are selected according to the actual products of the plant, but the seven-lump one is included of lumps which are partitioned based on the specified initial and final boiling points.For both approaches, a complete kinetic network with the catalyst-decay functions is considered. It is found that over a 17-month period of operation from the start of run, the average absolute deviation (AAD%) of the six-lump and the seven-lump models for the yield prediction are 20.51% and 5.21%, respectively for all products. Additionally, the sum of residuals for the seven-lump model has been appreciably decreased in comparison to the six-lump one. Therefore, it is confirmed that partitioning of the products to the lumps with specific boiling points can acceptably decrease the deviation of the prediction. So it is conclusive that including the operation of the separation section in commercial models can effectively increase the accuracy of the model and smooth the prediction error.

Recent Research Progress of Red Phosphors for PDPs Applications

AbstractThe commercial vacuum ultraviolet (VUV) red phosphor (Y, Gd)BO3:Eu3+ has low luminous efficiency and poor color purity. Our work aims to overcome this drawback and we mainly devote to investigating the luminescence mechanism, improving the commercial red phosphor, and seeking for new red emitting VUV materials with high efficiency. Based on the investigation of the photoluminescence mechanism of VUV phosphors, both the luminous efficiency and the color purity of (Y, Gd)BO3:Eu3+ are improved. Additionally, a series of novel VUV red phosphors have been developed, such as (Gd,Y)Al3(BO3)4:Eu3+ and (La,Gd)P3O9:Eu3+. This presentation is a review about the recent research progress of red phosphors for plasma displays (PDPs) applications in our group.

Comparison between fixed fluidized bed (FFB) and batch fluidized bed reactors in the evaluation of FCC catalysts

The laboratory reactors ACE fixed fluidized bed FFB and batch fluidized bed CREC Riser Simulator were compared in the conversion of two commercial vacuum gas oil feedstocks (paraffinic and aromatic types) over two equilibrium commercial FCC catalysts (octane-barrel and resid types) under similar conditions. Reaction temperatures were 510 and 540°C and the catalyst to oil mass ratios were from 4 to 9 in the FFB unit, with time on stream varying from 112 to 50s, and 6.35 in the CREC Riser Simulator, with reaction times ranging from 5 to 25s. The results were contrasted in some cases to those of a DCR circulating pilot plant unit at 540°C.When the different product yields were considered, the same catalyst ranking was observed in both laboratory reactors on the whole, differences between catalysts and particularly between feedstocks being more perceptible in the FFB reactor. The CREC Riser Simulator reactor showed a linear yield curve for gasoline, which facilitated the analysis and comparisons; in this case, an overcracking regime was not shown, like in the case of the FFB reactor. The LCO yield curves were more defined and differences between catalysts developed more clearly in the FFB reactor. Coke yields were very high in the FFB reactor, typical of confined beds with continuous feed of the reactants, while in the CREC Riser Simulator reactor they were in the range of those observed in the pilot plant and commercial units.The two laboratory reactors showed complementing potential in the laboratory evaluation of commercial catalysts and feedstocks for the FCC process.

Effects of molybdenum content on the structure and mechanical properties of as-cast Ti–10Zr-based alloys for biomedical applications

The effects of molybdenum on the structure and mechanical properties of a Ti–10Zr-based system were studied with an emphasis on improving the strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti–10Zr and a series of Ti–10Zr–xMo (x=1, 3, 5, 7.5, 10, 12.5, 15, 17.5 and 20wt.%) alloys prepared using a commercial arc-melting vacuum pressure casting system were investigated. X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer. Three-point bending tests were performed to evaluate the mechanical properties of all specimens. The experimental results indicated that these alloys had different structures and mechanical properties when various amounts of Mo were added. The as-cast Ti–10Zr has a hexagonal α′ phase, and when 1wt.% Mo was introduced into the Ti–10Zr alloy, the structure remained essentially unchanged. However, with 3 or 5wt.%, the martensitic α″ structure was found. When increased to 7.5wt.% or greater, retention of the metastable β phase began. The ω phase was observed only in the Ti–10Zr–7.5Mo alloy. Among all Ti–10Zr-xMo alloys, the α″-phase Ti–10Zr–5Mo alloy had the lowest elastic modulus. It is noteworthy that all the Ti–10Zr and Ti–10Zr–xMo alloys had good ductility. In addition, the Ti–10Zr–5Mo and Ti–10Zr–12.5Mo alloys exhibited higher bending strength/modulus ratios at 20.1 and 20.4, respectively. Furthermore, the elastically recoverable angles of these two alloys (26.4° and 24.6°, respectively) were much greater than those of c.p. Ti (2.7°). Given the importance of these properties for implant materials, the low modulus, excellent elastic recovery capability and high strength/modulus ratio of α″ phase Ti–10Zr–5Mo and β phase Ti–10Zr–12.5Mo alloys appear to make them promising candidates.

Cathode Spot Dynamics and Arc Structure in a Dense Axial Magnetic-Field-Stabilized Vacuum Arc

The structures of cathode roots on axial magnetic field (AMF)-stabilized contacts at gap distances of a few millimeters are investigated by observation of the arc behavior with a high-speed high-resolution electronic camera. While the current that is carried by a single cathode spot is almost independent of the arc current, the number of cathode spots and the voltage drop between the contacts linearly increase with the total current. At the limit of the breaking capability of the contacts, the average current density is about 1.8 (effective current), which conforms well to the experience with commercial vacuum interrupters. At this point, the CuCr contact surface homogeneously melts over several tenths of square centimeters. Although the molten surface layer thickness is assumed to be a few tens to hundreds of micrometers at most, millimeter-sized protrusions rapidly grow, providing the impression of a “boiling” surface. The growth and dynamics of these surface structures are discussed and compared with the details of spatial-temporal measurements, and an explanation is given for the high rates of acceleration of droplets in the radial direction.